Positional terms such as “rear” or “top”, “right” or “left” are used in this patent with reference to a weapon positioned in a shooting position, That is, with reference to a weapon positioned to shoot “forward” (i.e., away from the shooter), in a generally horizontal plane.
Conventional light weight machine guns often have a carrying handle that is mounted near the rear end of the barrel, (i.e., in proximity to the gun's center of gravity). The handle can be moved between a rest position and a working position. In the rest position, the carrying handle is folded down and rests against the jacket of the machine gun. In its working position, the carrying handle protrudes upwards from the machine gun and is positioned to serve for transporting the gun.
In general, such machine guns should be as light as possible and be able to handle long rounds and a high overall number of shots. Each shot fired produces heat and the gun barrel may become over-heated during use. To address this issue, these machine guns usually have devices that allow one to quickly exchange one barrel for another.
Such devices are usually designed as latches that snap into place. After the latch is opened, the barrel can be removed, for example, with asbestos-clad gloves or by means of a heat-insulated manual handle (see CH 116,607). Subsequently, a new barrel is inserted, and the latch is closed again. In its closed position, the latch should be firmly locked and hold the barrel in its proper position during the next round of firing.
There are several disadvantages with the above described prior art design. First, if the asbestos-clad gloves are not within easy reach or if there is a failure, the machine gun operator may inadvertently use his free hand to remove the hot barrel and injure himself. Second, in the excitement of a fight, it is easy to forget about the need to always carefully check and make sure that the latch is properly locked. If the latch is not properly locked, it could unexpectedly open, thereby permitting the barrel to fall out of the gun. One could conceive of a separate safety catch that would only allow the gun to fire when the latch has properly snapped into place. However, such a safety catch would disable the weapon if the barrel becomes loose and, at any rate, would be very complicated and, thus prone to failure.
It would also be possible to equip the snap-in latch with a secondary latch. However, such a secondary latch would require additional operations to exchange a barrel and, thus, delay and complicate the exchange process.
Detachable barrels on machine guns with carrying handles are known in the prior art. For example, U.S. Pat. No. 2,131,716 illustrates a device for removal and/or insertion of a barrel that can be provided in addition to a carrying handle on a machine gun. However, the actuation of the device shown in U.S. Pat. No. 2,131,716 is independent from the position of the carrying handle and/or can only occur when the carrying handle is in position B (see FIG. 2 of U.S. Pat. No. 2,131,716).
A transversally arranged eccentric rod used to hold a barrel of an automatic firearm in a detachable connection is known from U.S. Pat. No. 2,423,854.